1. Technical Field
The present invention relates to a technology which prints an image which includes a multi-layered ink layer.
2. Related Art
As one of ink jet printers, a serial-type ink jet printer has been known that forms an image by discharging ink from a print head while moving the print head in the main scan direction and the sub scan direction. In addition, a technology has been known that prints an image which includes a multi-layered ink layer using the ink jet printer.
For example, JP-A-2006-247991 discloses a technology that forms an under layer on a transparent printing medium using white ink, and performs printing on the formed under layer using process color ink. In addition, JP-A-2006-247991 discloses a technology (hereinafter, referred to as a nozzle division technology) that discharges one of the white ink and the process color ink using an upper stream side nozzle group of nozzle columns which are formed on the print head for each kind of ink, and discharges the other side ink using a downstream side nozzle group. According to the nozzle division technology, it is possible to form a two-layered ink layer while the printing medium is transported one time throughout the length of the printing medium.
JP-A-2001-1560, WO 2005/105452, and JP-A-5-64870 are examples of the related art.
When a print matter which includes a five or more-layered ink layer is printed using such a multi-layer printing technology, various problems may occur. The print matter which includes the five or more-layered ink layer can employ a print matter in which, for example, a first color layer which is formed by color ink, a first specific gloss layer which is formed by specific gloss ink, an under layer which is formed by white ink, a second specific gloss layer which is formed by the specific gloss ink, and a second color layer which is formed by the color ink are formed on the transparent printing medium. The specific gloss ink is ink which reveals specific gloss such as metallic texture. The print matter can employ a print matter which enables an image to be visible from both surfaces of the printing medium.
However, when five layers are formed on one side surface of the printing medium, if the five layers are configured in such a way that a nozzle column is divided into five nozzle groups using the above-described nozzle division technology and each of the nozzle groups obtained through the division forms a single layer, the number of nozzles for each single nozzle group obtained through division becomes small. As a result, a range which can be printed using a single nozzle group becomes small, and thus a printing speed becomes extremely slow.
On the other hand, when the nozzle division technology is not used, only a single-layered ink layer is formed during a process to transport the printing medium one time throughout the length of the printing medium. Therefore, in order to form a five-layered ink layer, it is necessary to repeat the process five times. With regard to the repetition of the process to transport the printing medium, a method of automatically reversing the feed direction of the printing medium and a method of repeatedly setting the printing medium to an initial position by a manual operation are conceivable. In both methods, it is difficult to avoid the slight deviation of the position of the printing medium during a plurality of transport processes. That is, the relative position of each layer of the print surface is deviated from a prescribed original position. For example, if the positional relationship between the first color layer and the first specific gloss layer is deviated, the feeling of specific gloss to be revealed varies. As a result, there is a problem in that the deterioration of print quality may occur.
In addition, when three layers are formed on one side surface of the printing medium and two layers are formed on the other side surface, there is a case in which a problem occurs as a result that both the side surfaces of the printing medium are printed. For example, when a print matter, both side surfaces of which are printed, comes into contact with the window of a premise such that printed content can be viewed from either on or off the premise, a printed surface of one side is directly pasted on the window. In this case, there is a problem in that ink adheres to the window. That is, when the pasted print matter is taken off, it is necessary to remove the adhered ink.